1) A large powerful animal, kept as a watch dog. It was subject to certain restrictions.
1573 if any man do keep any mastiffs unmuzzled of the day or going abroad in the street of the night he shall forfeit iijs ivd, Doncaster
1648 Mitchell continues as froward as ever, but I threatening to kill his mastive hee sent her home, Thurlstone
1672 did give out threatning words against her children ... would pull them in peeces with his mastie-dog, Lightcliffe. In c.1615 a pain was laid in the Knaresborough court that Jane Woodward ... put away a mongrell mastie ... beinge an unruly dogg and her children dogginge of men’s goodes [cattle] with him ... upon the King’s common.